System and method for periodic ranging in a sleep mode in a BWA communication system

1. A method for performing a periodic ranging by a receiver in a sleep mode of a wireless communication system, the method comprising the steps of:

receiving a sleep mode transition message to transit into a sleep mode, the sleep mode transition message including first information relating to a timing point at which the periodic ranging is performed;

transiting to the sleep mode in response to the sleep mode transition message; and

performing the periodic ranging at a timing point corresponding to the first information after transiting to the sleep mode,

wherein the first information indicates an offset of a frame in which the periodic ranging will be performed with respect to a frame where the sleep mode transition message is transmitted.

2. The method as claimed in claim 1 , wherein performing the periodic ranging comprises:

transiting from the sleep mode to an awake mode if the receiver stays in the sleep mode at the timing point corresponding to the first information; and

performing the periodic ranging after transiting to the awake mode.

3. The method as claimed in claim 2 , further comprising:

receiving a periodic ranging completion notification including second information relating to a timing point at which a next periodic ranging is performed; and

transiting from the awake mode to the sleep mode when a timing point at which the periodic ranging completion notification has been received is identical to a timing point corresponding to the sleep mode.

4. The method as claimed in claim 3 , further comprising a step of maintaining the awake mode when the timing point at which the periodic ranging completion notification has been received is not identical to the timing point corresponding to the sleep mode.

5. The method as claimed in claim 3 , wherein the second information includes a time offset between the timing point at which the periodic ranging completion notification has been received and the timing point at which the next periodic ranging is performed.

6. The method as claimed in claim 1 , further comprising:

performing the periodic ranging in an awake mode if when the receiver stays in the awake mode at the timing point corresponding to the first information.

7. The method as claimed in claim 6 , further comprising:

receiving a periodic ranging completion notification including second information relating to a timing point at which a next periodic ranging is performed, while the periodic ranging in the awake mode is performed; and

transiting from the awake mode to the sleep mode when a timing point at which the periodic ranging completion notification has been received is identical to a timing point corresponding to the sleep mode,

wherein the second information indicates a time offset between a frame at which the periodic ranging completion notification has been received and a frame at which the next periodic ranging is performed.

8. The method as claimed in claim 7 , further comprising:

maintaining the awake mode when the timing point at which the periodic ranging completion notification has been received is not identical to the timing point in time corresponding to the sleep mode.

9. A method for performing a periodic ranging by a transmitter in a sleep mode of a wireless communication system, the method comprising the steps of:

transmitting a sleep mode transition message to transit into a sleep mode of a receiver, the sleep mode transition message including first information relating to a timing point at which the periodic ranging is performed; and

performing the periodic ranging with the receiver that has transited into the sleep mode, at a timing point corresponding to the first information, after transmitting the sleep mode transition message,

wherein the first information indicates an offset of a frame in which the periodic ranging will be performed with respect to a frame where the sleep mode transmission message is transmitted.

10. The method as claimed in claim 9 , wherein performing the periodic ranging comprises:

transmitting a periodic ranging completion notification including second information relating to a timing point at which a next periodic ranging is performed, when it is determined that the periodic ranging in progress must be completed.

11. The method as claimed in claim 10 , wherein the second information includes a time offset between a timing point at which a receiver receives the periodic ranging completion notification and the timing point at which the next periodic ranging is performed.

12. A system for performing a periodic ranging in a sleep mode of a wireless communication system, the system comprising:

a transmitter for transmitting a sleep mode transition message to transit into a sleep mode, the sleep mode transition message including first information relating to a timing point at which the periodic ranging is performed; and

a receiver for transiting to the sleep mode in response to the sleep mode transition message, and performing the periodic ranging at a timing point corresponding to the first information after transiting to the sleep mode,

wherein the first information indicates an offset of a frame in which the periodic ranging will be performed with respect to a frame where the sleep mode transition message is transmitted.

13. The system as claimed in claim 12 , wherein the receiver transits from the sleep mode to an awake mode if the receiver stays in the sleep mode at the timing point cooresponding to the first information and performs the periodic ranging after transiting to the awake mode.

14. The system as claimed in claim 12 , wherein the transmitter transmits a periodic ranging completion notification including second information relating to a timing point at which a next periodic ranging is performed when the transmitter determines that the periodic ranging in progress must be completed.

15. The system as claimed in claim 14 , wherein, after receiving the periodic ranging completion notification while the periodic ranging is performed, the receiver transits from the awake mode to the sleep mode when a timing point at which the receiver has received the periodic ranging completion notification is identical to a timing point corresponding to the sleep mode.

16. The system as claimed in claim 15 , wherein the receiver maintains the awake mode when the timing point at which the receiver has received the periodic ranging completion notification is not identical to the timing point corresponding to the sleep mode.

17. The system as claimed in claim 16 , wherein the second information includes a time offset between the timing point at which the periodic ranging completion notification has been received and the timing point at which the next periodic ranging is performed.

18. A method for performing a periodic ranging by a receiver in a sleep mode of a wireless communication system, the method comprising the steps of:

receiving a ranging response message to transit into a sleep mode, the ranging response message including first information relating to a timing point at which the periodic ranging is performed; and

transiting to the sleep mode in response to the ranging response message; and

performing the periodic ranging at a timing point corresponding to the first information after transiting to the sleep mode,

wherein the first information indicates an offset of a frame in which the periodic ranging will be performed with respect to a frame where the ranging response message is transmitted.

19. The method as claimed in claim 18 , wherein the ranging response message includes the first information and a ranging status set to success.